.TH std::ranges::view_interface::back 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::ranges::view_interface::back \- std::ranges::view_interface::back

.SH Synopsis
   constexpr decltype(auto) back()
       requires ranges::bidirectional_range<D> &&                     \fB(1)\fP \fI(since C++20)\fP
   ranges::common_range<D>;
   constexpr decltype(auto) back() const
       requires ranges::bidirectional_range<const D> &&               \fB(2)\fP \fI(since C++20)\fP
   ranges::common_range<const D>;

   The default implementation of back() member function returns the last element in the
   view of the derived type. Whether the element is returned by value or by reference
   depends on the operator* of the iterator type.

   1) Let derived be static_cast<D&>(*this). Equivalent to return
   *ranges::prev(ranges::end(derived));. The behavior is undefined if empty() is true
   (i.e. the beginning iterator compares equal to the sentinel), even if the iterator
   obtained in the same way is dereferenceable.
   2) Same as \fB(1)\fP, except that derived is static_cast<const D&>(*this).

.SH Parameters

   \fI(none)\fP

.SH Return value

   The last element in the view.

.SH Notes

   In C++20, no type derived from std::ranges::view_interface in the standard library
   provides their own back() member function.

   However, following derived types cannot use the default implementations, as they
   never satisfy neither bidirectional_range nor common_range:

     * std::ranges::basic_istream_view
     * std::ranges::lazy_split_view
     * std::ranges::split_view
     * std::ranges::take_while_view

   The inherited back() member function is available for std::ranges::empty_view, but a
   call to it always results in undefined behavior.

.SH Example

    This section is incomplete
    Reason: no example

.SH See also

   rbegin          returns a reverse iterator to the beginning of a container or array
   crbegin         \fI(function template)\fP
   \fI(C++14)\fP
   ranges::rbegin  returns a reverse iterator to a range
   (C++20)         (customization point object)
   ranges::crbegin returns a reverse iterator to a read-only range
   (C++20)         (customization point object)

.SH Category:
     * Todo no example
